I916. No. 10. THE LOWER CAMBRIAN HOLMIA FAUNA. 4I 



Ellipsocephalus Zenker. 



The type of this family is the old and well-known Bohemian form 

 Ellipsocephalus Hoffi Schlotheim, that is so common in the famous fossili- 

 ferous Paradoxides shales at Skrej that it is probably found in all museums. 

 This and several other Middle Cambrian tbrms exhibit a \-erv marked 

 peculiarity, which characterised the genus, viz. a glabella of almost even 

 breadth, although slightly drawn in between the palpebral lobes, the glabella 

 also being angularh' pointed at the anterior, the occipital ring also being 

 either entirely or almost effaced. The position and form oï the palpebral 

 lobes, and the short posterior branch of the facial suture agree entirelv 

 with Strenuella. In the older forms the first peculiaritys disappear more 

 and more. The occipital ring becomes distinctly marked and the glabella 

 assumes a more Strenuella- like form. This is especialiv so in the case of 

 the forms in the Scandinavian Lower Cambrian, and which have been 

 referred to Ellipsocephalus , but which in reality might just as well be 

 regarded as Strenuella Matthew. As however, in the latter, the trans- 

 formation of the glabella in an Ellipsocephalid direction has commenced, 

 and that transformation can be pursued to the typical Middle Cambrian 

 species, we appear to be justified in uniting the whole of this series into 

 one genus, the limitations o\ which towards Strenuella thus become uncertain. 



Ellipsocephalus Nordenskjöldi Lnrs. 

 (PI. IV, figs. 7—8, pi. V. figs. II— 13I. 



1873. Arioiiellus sp. pp. Th. Kjerulf, Sparagmittjeldet, Pag. 83, fig. 6. 



Illustration of head shield of this form as Arionellus sp. 

 1883. Ellipsoceplialus Nordenskjöldi, Linnwrsson. De undre Paradoxides lagren vid Andrarum, 

 (Sveriges Geol. Unders. Ser. C. Xo. 54, pag. 21, PI. IV, fig. 1.1. 



Describes and depicts this form from the Graavakke shales at Andrarum. Fig. 2 

 as mentioned by C. Wimax ^ is not this form. In the present work it is regarded as 

 Strenuella Linnarssoni nov. sp. 



Description: Only cranidiums without free cheeks are known of 

 this form. The Cranidium is comparatively flat, and its length is conside- 

 rably less than the breadth (without free cheeks). The Gl ab el la is sharply 

 marked but without distinct dorsal furrows; in smaller specimens it is 

 comparatively strongly arched, whilst in larger ones it is flatter, it is 

 almost of even breadth, with nearly parallel sides, the anterior region being 

 rounded or slightly pointed to an angle. There are three pairs of faint 

 but distinct furrows; the most posterior ones are more bent backwards 



1 Studien über das nordbak. Silurgebiet i (Bull, of the Geol. Inst, of Uppsala, Vol. VI, 

 igo2, page 441. 



